The present invention relates to an improved device for the administration of drugs. More particularly, the invention relates to an improved device for subcutaneous introduction of drug implants and to a novel shaped implant dosage form for use in such device.
Techniques and devices for introducing solid medicaments beneath the skin are known in the art. Medical use of drug implants was initiated as early as 1861, see Howard Jones, N., J. Hist. Med. 2, 201 (1947).
Implants have advantageously been used for administration of hormones, such as testosterone, estradiol and other drugs, where slow, constant release and continuous absorption of a drug over prolonged time periods is desired. The long lasting effect of a drug implant frees the patient from the need to take multiple periodic parenteral or oral doses. In the long run, implant therapy is often more economical. Moreover, where a dosage regimen is critical, use of implants eliminates the possibility of missed doses. Though clinical use of pellet implants has declined with the development of oral dosage forms, it nevertheless remains a valuable medical tool in, for example, drug absorption studies. Surface area of an implant is readily determined and controlled. Moreover, the effective area of a pellet in contact with body tissues can be measured, before and after implantation, by simple direct inspection of the implant.
As stated heretofore, devices for subcutaneous introduction of implants are disclosed in the prior art. One such device comprises an injector needle, having a central longitudinal axial bore and a sharp beveled end, a first plunger having a sharp beveled end and a second plunger having a blunt end. The first plunger and the second plunger are each removably insertable within the bore of the injector needle. The technique employed with this prior art device is as follows:
The area wherein the pellet is to be inserted is anesthetized with a local anesthetic. A small incision is made in the skin to permit free passage of the injector needle. The first plunger is inserted into the bore of the injector needle, then the injector needle, with the first plunger in place, is inserted into the subcutaneous tissue. When insertion of the injector needle is complete the first plunger is withdrawn from the bore. A drug pellet is then introduced into the injector bore and gently forced down the bore and into the subcutaneous tissues with the blunt end of the second plunger. Once the pellet is fully inserted, the injector and the second plunger seated in the bore are simultaneously withdrawn. The incision is then closed with sutures, a clip, or an adhesive bridge etc.
The aforementioned prior art device suffers from several major defects and has not proven successful. Firstly, a preliminary surgical incision is required before the device can be employed. Secondly, if upon insertion into the subcutaneous tissues, the injector needle, with the first plunger in place, is not properly oriented, that is to say, the beveled sharp end of the first plunger is not in alignment with the beveled sharp end of the injector needle, insertion of the device will result in considerable tearing of the tissues.
U.S. Pat. No. 3,921,632 discloses an improvement over the above-described prior art device. Use of such improved device obviates the need for preliminary surgical incision. The device of such patent makes a clean incision. No stitching or sutures are generally thereafter required. Furthermore, in the device of such patent, means are provided for preventing improper orientation of the sharp end of the injector needle and the sharp end of the first plunger so that disadvantageous tearing of the skin and tissues is avoided.
The device of U.S. Pat. No. 3,921,632 comprises: a tubular member having a central longitudinal axial bore therethrough, a pointed elongated annular concavely beveled implanting end and a charging end. The implanting and charging ends communicate with the bore. A first plunger having a solid pointed elongated annular concavely beveled end is adapted to be removably inserted in the bore for slidable movement therein. When the first plunger is completely inserted in the bore of the tubular member the beveled implanting end of the tubular member and the beveled end of the first plunger are aligned to form a complimentary substantially continuous, pointed, elongated, annular concavely beveled penetration surface. The first plunger is slidably moveable in the bore of the tubular member from a first to a second position at which insertion of the plunger in the bore is complete. Means are also provided for permitting the alignment at only the second position. As is shown in FIG. 4 of the patent, a second plunger having a blunt tip is also provided. The device of U.S. Pat. No. 3,921,632 works as follows:
As is seen from FIG. 1 of the patent, the first plunger 6 is introduced into the bore of the tubular member and when fully introduced the ends (elements 9, 3, and 10) are in alignment. This is more clearly shown in FIG. 2 of the patent. The cannula of the device is then injected into the patient. After it is introduced the first plunger is slidably removed from the bore and a pellet implant is inserted into the bore. The blunt ended plunger is then employed to push the pellet through the bore and into the subcutaneous tissues of the patient.
The present invention presents improvements on the above-described device of U.S. Pat. No. 3,921,632.
The implant device of the present invention can advantageously be made of metal, such as stainless steel, or of plastic and stainless steel and can be sterilized by steam or radiation. Most desirably, with the exception of the cannula, all parts are made of plastic so that the device is less costly and disposable.
A further advantage of the improved device of the present invention is that it contains fewer parts than the device of U.S. Pat. No. 3,921,632. There is no need for the blunt plunger 16 of such patent. Moreover, the device of the present invention can be preloaded with one or more pellet implants. This is possible because of the novel form of the solid dosage form of the present implant device.
As will be more fully described later on in this disclosure, the present invention provides a solid implant dosage form that is shaped so that when it is in the bore of the injector needle and positioned at its end, a face of the solid dosage form aligns with the beveled end of the injector needle so as to present a complimentary elongated annular concave surface